Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
Hector Gomez - California State University, Los Angeles
Co-Author(s): Arturo Pacheco-Vega, California State University, Los Angeles
A three-dimensional laminar flow-based fuel cell (LFFC) numerical simulation has been carried out to find the current-voltage distribution and power density through a channel. The system is a Y-shaped LFFC with two separate inlets, where fuel and oxidant enter and flow in parallel alongside each other. A novel geometry (based on a sinusoidal function, i.e., a wavy channel) has been implemented and tested numerically to increase the performance of the fuel cell system. The LFFC uses formic acid and oxygen, saturated in sulfuric acid, as the fuel and oxidant, respectively. The aim is to analyze the effects of wavy channel compared to a straight channel on the performance of LFFCs. The amplitude is varied from 0.1 to 0.5. A second set of experiments will demonstrate the results of integrating harmonics into the wavy channel. In addition to the wavy channel comparison, the second aim is to analyze the effects of operating conditions and geometrical parameters on the performance of LFFCs. The width (2mm), length (5cm), and inlet angle (45⁰) were varied from 1mm to 3mm, 3cm to 6cm and 0⁰ to 180⁰, respectively, with channel aspect ratio obtained from literature. The inlet velocity (from 0.1 to 6 mm/s) and inlet concentrations of formic acid (from 1M to 15M) at the anolyte and oxygen (from 50mM to 200mM) at the catholyte channels were varied. The governing equations are given in terms of the Navier-Stokes, Butler-Volmer and conservation of species along with Darcy’s equation to model the flow absorbed by the porous electrodes, and are solved using the finite element method. At low Reynolds number, they exploit the lack of turbulent and convective mixing, allowing the fuel and oxidant to travel side by side reacting at the electrodes. The mathematical model was verified with published experimental work. Results were obtained in the form of polarization curves and power density graphs. We have demonstrated that the wavy channel LFFC systems had better performance due to the reduction in diffusion and depletion boundary layers. The concentration fields also demonstrated the correlation between the increase in diffusion and depletion boundary layers and the decrease in power density. We have also shown that LFFC systems with higher fluid velocities and oxygen concentration significantly improve the power densities. However, when the fuel concentration was increased, the cell performance had insignificant impact compared to the other operating conditions.
Funder Acknowledgement(s): CSULA LSAMP-BD NSF under Grant #HRD-1363399.
Faculty Advisor: Arturo Pacheco-Vega, firstname.lastname@example.org
Role: I performed the numerical simulations, obtained the results and post results analysis.